I'm creating a sandbox and wanted to give importance to the weather. I didn't find anything about the effect of extreme temperatures on ars magica (except "sensitive to cold" and "sensitive to heat" in RoP:M), so I decided to create my own guidelines, inspirated by the climate guidelines I found in a spanish book sandbox creation titled "hexplora".
The idea is that clothing, natural resistence, magic, etc. gives you points in "cold protection" or "heat protectiont". If you have enough protection for the current temperature, you are fine. If you have partial protection, you will have a rought time. And if you are unprotected: good luck.
Since the saga will be set in the territory that is current Estonia and Finland, I started with the cold aspect.
I'm new in ars magica, so things are probably very wrong (I don't know if auram should grant base protection or just ignem, for exemple. Maybe the temperature shouldn't cause cold damage and only cause fatigue...).
I made fatigue direct (without fatigue test) like a long-term fatigue. But maybe I should allow a test?
I'm not sure about your cold labels. I had a ski race in -40° equivalent conditions once. And that was in a relatively warm region for skiing. Now, that did include wind chill. But, as I said, that was a warm ski region. Lapland's ambient temperature can get down to -50°C or so, ignoring the wind chill on top of that.
Also, CrIg +5 damage is the same level base as boiling water. The Ignem 30 you're requiring is way beyond that, even well beyond making things glow red hot. But you're not even allowing that to grant complete protection against lower temperatures.
Maybe I explained it wrongly. The "maga o magus with ignem or Auram 30" referes that he or she has 30 points in that art. Obviusly, lower level spell could grant a good protection, but well-trained ignem old magus could walk in the middle of the arctic almost naked without any spells afecting him, only thanks to his resistence to cold thanks to ignem.
Out of curiosity, I looked up the lowest temperature records 68°C two times in Siberia in the 20th century. That's the lowest recorded where humans normally live. I figure we can discount things like Antarctic lows for Ars Magica.
Okay, I updated the info so that is not the same going completely naked to Siberia as to go with some clothes on:
Now, our well-equipped Siberian peasant (with a +2 in proteccion for the winter clothes + fur clothing) will receive 1 fatigue for every hour in the -68ºC you are talking about.
Yes, the numbers don't seem unreasonable. I just mentioned the label for the low temperatures, since there are people used feeling these temperatures infrequently.
Callen's mention of wind chill is really important. Wind is a huge factor in staying warm. I'll wear the same number of layers in windy near 0C weather as I will in calm -15C weather.
On the other side, humidity really affects how people deal with hot weather - 40C and dry is more bearable than 30C and 100% humidity.
An official system dealing with this is found in Rival Magic p105 in the "Exposure and Frostbite" sidebar - having wizards who deal with frost giants, and their supernatural ability dealing with cold, made it necessary to have some rules.
I have a feeling that Tales of Power might be your friend, as travelling to the City of Brass required my covenant to develop spells to deflect desert sunlight and protect ourselves against heat.
Looks like ToP (p.48), BSaS (p.66), and LotN (p.10) have matching rules. These rules are more limited than the cold-temperature rules. Happily, they're in agreement at reference the core rules.
There's some subjectivity here as people from hotter or colder climates will experience temperatures differently. As well, there is a difference between wet vs dry heat or cold, and day vs night. Colder weather with the sun on your feels much different than the same temperature in the dead of night.
